In a citywide effort Saturday to try to curb the violence on Chicago streets, police collected more than 4,000 guns and other weapons in exchange for gift cards worth up to $100.

Residents frustrated by the gun violence that has long plagued their neighborhoods marched through the streets, many of them bereaved mothers who recited poems, sang songs and prayed for an end to the shooting.

"No mother should have to bury a son," said Vallie Smith, whose son, Mario Hines, 21, was shot to death in March. Hines had been arrested in 2007 for illegally carrying a handgun himself.

His mother joined about 100 demonstrators marching through a patch of Ashburn where there have been several recent shootings. The Southwest Side neighborhood was among 22 sites were guns were collected Saturday, with a total of 4,050 handed in by the end of the day, Chicago police said. Fifty-five were assault weapons, 3,335 were handguns and there were 660 fake replicas.

"We have to get the guns and gangs out of here," Smith said. "Whoever did this to my son, I hope their mother doesn't ever have to feel this pain."

Collecting guns from their owners may seem like a futile effort to skeptics, since those voluntarily turning in their weapons are likely not the ones behind neighborhood violence that has devastated some communities, acknowledged Chicago Police Superintendent Jody Weis. But the program nonetheless means there are fewer weapons around that could somehow end up in the wrong hands, he said.

"We have just too many guns in our society," said Mayor Richard Daley, speaking before a march in Old Town, on the Near North Side. "When someone has access to a gun, they use it."

As he spoke to those gathered, Daley argued for tighter gun control, estimating that about a million Americans have lost their lives to gun violence since Martin Luther King Jr.'s assassination in 1968.

The gun exchange program is in its sixth year and is credited with taking thousands of weapons off the streets.

Saturday's take represented a mix of firepower. Besides the hand grenades, which police said were inert, some people handed in dusty antique rifles, while others gave up their high-performance rifles. Some of the guns collected are so deadly, they could pierce bulletproof vests, Weis said.

Those turning in actual guns got $100 gift cards and lower-value gift cards for BB guns and toy replica guns. At St. Sabina Church, on the South Side, the church gave an extra $50 for assault weapons.

Glancing at the tables of weapons, the parents of murdered children became emotional.

"Our children were all innocent when they were taken," said Denise Reed, the mother of Starkesia Reed, a 14-year-old honor student who was killed in 2006 when a stray bullet hit her in the head while she was inside her Englewood home.

Reed pointed to the tables of guns and said for the parents each weapon represents a life.

"We feel like it's a life that has been saved," she said. "That could be 3,000 lives that the city of Chicago will not have to bury."

Annette Nance-Holt said she would be satisfied saving just one life. Her son Blair Holt was killed in 2007 when he tried to shield another student on his CTA bus from gunfire. She said she doesn't look forward to Mother's Day because it comes just after the anniversary of her then-16-year-old's death.

"Every day is hard, but Mother's Day is particularly hard for me," she said.